Scroll fluid machine

ABSTRACT

Lubricant is satisfactorily supplied to a bearing that supports an eccentric bush. A scroll compressor (100) includes a fixed scroll (122) fixed to a housing (140), an orbiting scroll (124) that orbits with respect to the fixed scroll, and a conversion mechanism (300) that mutually converts a rotary motion of a drive shaft (166) and an orbiting motion of the orbiting scroll. The converting mechanism includes an eccentric shaft (260) that is provided on an end surface of the drive shaft and is eccentric with respect to the drive shaft, an eccentric bush (270) having a through hole (271) into which the eccentric shaft is fitted, and a bearing (280) that is press-fitted into a boss portion (250) formed on the orbiting scroll and supports an outer peripheral surface (272) of the eccentric bush. A lubricant supply passage (350) for supplying lubricant to the bearing is penetratingly formed in the eccentric bush. An outlet (356) of the lubricant supply passage is disposed on the outer peripheral surface of the eccentric bush (272).

TECHNICAL FIELD

The present invention relates to a scroll fluid machine such as a scrollcompressor and a scroll expander.

BACKGROUND ART

Patent Document 1 discloses a scroll compressor which is an example of ascroll fluid machine. In this scroll compressor, a drive shaft isconnected to an orbiting scroll via a crank mechanism. The crankmechanism includes a boss portion formed on a back pressure chamber sideend surface of a bottom plate of the orbiting scroll and an eccentricbush eccentrically attached to a crank pin disposed at an end portion ofthe drive shaft. The eccentric bush is rotatably supported by an innerperipheral surface of the boss portion via a bearing.

REFERENCE DOCUMENT LIST Patent Document

-   Patent Document 1: JP 2019-015188 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

Lubrication of the aforementioned bearing is achieved by dispersinglubricant in the back pressure chamber formed on the rear surface sideof the orbiting scroll, and as a result, supply of the lubricant to thebearing may become insufficient.

Thus, it is an object of the present invention to satisfactorily supplylubricant to a bearing supporting an eccentric bush.

Means for Solving the Problem

According to an aspect of the present invention, a scroll fluid machinehas, in a housing, a rotating main shaft that is rotatably provided, afixed scroll fixed to the housing, an orbiting scroll that orbits withrespect to the fixed scroll, and a conversion mechanism that mutuallyconverts a rotary motion of the rotating main shaft and an orbitingmotion of the orbiting scroll. The converting mechanism includes aneccentric shaft that is provided on an end surface of the rotating mainshaft and is eccentric with respect to the rotating main shaft, aneccentric bush having a through hole into which the eccentric shaft isfitted, and a bearing that is press-fitted into a boss portion formed onthe orbiting scroll and supports an outer peripheral surface of theeccentric bush.

A lubricant supply passage for supplying lubricant to the bearing ispenetratingly formed in the eccentric bush. Here, an outlet of thelubricant supply passage is disposed on the outer peripheral surface ofthe eccentric bush.

Effects of the Invention

According to an aspect of the present invention, the outlet of thelubricant supply passage is disposed on the outer peripheral surface ofthe eccentric bush. As a result, lubricant can be supplied directly fromthe outlet of the lubricant supply passage to the bearing, and thus, thelubricant can be satisfactorily supplied to the bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view of a scroll compressoraccording to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating how gaseous refrigerant andlubricant flow in the first embodiment.

FIG. 3 is an enlarged cross-sectional view of a conversion mechanismaccording to the first embodiment.

FIG. 4 is a perspective view of an eccentric bush according to the firstembodiment.

FIG. 5 is a sectional view of the eccentric bush according to the firstembodiment.

FIG. 6 is an enlarged cross-sectional view of a conversion mechanismaccording to a second embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be describedreferring to the accompanying drawings. Here, a case in which a scrollfluid machine according to the present invention is a scroll compressoris described. It is, however, apparent that the present invention isalso applicable to a scroll expander.

FIG. 1 is a longitudinal cross-sectional view of a scroll compressor 100according to a first embodiment of the present invention.

The scroll compressor 100 is incorporated, for example, in a refrigerantcircuit of an air conditioner for a vehicle, and compresses anddischarges gaseous refrigerant (fluid) drawn from a low-pressure side ofthe refrigerant circuit. The scroll compressor 100 includes a scrollunit 120, a housing 140 that internally includes a suction chamber H1and a discharge chamber H2 for gaseous refrigerant, an electric motor160 that drives the scroll unit 120, and an inverter 180 that drives andcontrols the electric motor 160. The scroll unit 120 may be driven, forexample, by an engine output instead of by the electric motor 160. Theinverter 180 may not be incorporated in the scroll compressor 100.

The scroll unit 120 includes a fixed scroll 122 and an orbiting scroll(movable scroll) 124 engaged with each other. The fixed scroll 122includes a disk-shaped bottom plate 122A and an involute-shaped(spiral-shaped) wrap 122B erected on one surface of the bottom plate122A. Like the fixed scroll 122, the orbiting scroll 124 includes adisk-shaped bottom plate 124A and an involute-shaped wrap 124B erectedon one surface of the bottom plate 124A. Here, being disk-shaped issatisfied with being visually recognizable as being disk-shaped, and mayhave an outer surface including, for example, a convex portion, aconcave portion, or a slit (regarding the shape, the same will beapplied hereinafter).

The fixed scroll 122 and the orbiting scroll 124 are disposed such thatthe wraps 122B and 124B are engaged with each other. Specifically, thefixed scroll 122 and the orbiting scroll 124 are disposed such that thetip of the wrap 122B of the fixed scroll 122 is in contact with the onesurface of the bottom plate 124A of the orbiting scroll 124, and the tipof the wrap 124B of the orbiting scroll 124 is in contact with the onesurface of the bottom plate 122A of the fixed scroll 122. A tip seal(not shown) is attached to each of the tips of the wraps 122B and 124B.

Furthermore, the fixed scroll 122 and the orbiting scroll 124 aredisposed such that the circumferential angles of the wraps 122B and 124Bare offset from each other and the sidewalls of the wraps 122B and 124Bare partially in contact with each other. As a result, a crescent-shapedsealed space functioning as a compression chamber H3 is formed betweenthe wrap 122B of the fixed scroll 122 and the wrap 124B of the orbitingscroll 124.

The orbiting scroll 124 orbits with respect to the fixed scroll 122. Theorbiting scroll 124 is disposed to be capable of revolving around anaxis of the fixed scroll 122 via a conversion mechanism 300, which willbe described later, in a state in which rotation of the orbiting scroll124 is prevented. Thus, the scroll unit 120 moves the compressionchamber H3 defined by the wrap 122B of the fixed scroll 122 and the wrap124B of the orbiting scroll 124 toward the center while graduallyreducing the volume of the compression chamber H3. As a result, thescroll unit 120 compresses the gaseous refrigerant drawn into thecompression chamber H3 from the outer end portions of the wraps 122B and124B.

The housing 140 has a front housing 142 for housing the electric motor160 and the inverter 180, a center housing 144 for housing the scrollunit 120, a rear housing 146, and an inverter cover 148. The fronthousing 142, the center housing 144, the rear housing 146, and theinverter cover 148 are integrally fastened, for example, by at least onefastener (not shown) including a bolt and a washer, so as to constitutethe housing 140 of the scroll compressor 100.

The front housing 142 has a cylindrical peripheral wall portion 142A anda thin plate-like partition wall portion 142B. The internal space of thefront housing 142 is partitioned by the partition wall portion 142B intoa space for housing the electric motor 160 and a space for housing theinverter 180. One end side of the peripheral wall portion 142A, i.e., anopening of the space for housing the inverter 180, is closed by theinverter cover 148. The other end side of the peripheral wall portion142A, i.e., an opening of the space for housing the electric motor 160,is closed by the center housing 144. At a radially center portion of thepartition wall portion 142B, a cylindrical support portion 142B1protruding toward the other end side of the peripheral wall portion 142Ais provided. The support portion 142B1 rotatably supports one endportion of a drive shaft 166, which will be described later. Here, thedrive shaft 166 is an example of the “rotating main shaft” of thepresent invention, and it is rotatably provided in the housing 140.

Furthermore, the suction chamber H1 for gaseous refrigerant is definedby the peripheral wall portion 142A and the partition wall portion 142Bof the front housing 142, and the center housing 144. Gaseousrefrigerant is drawn from the low-pressure side of the refrigerantcircuit into the suction chamber H1 via a suction port P1 formed on theperipheral wall portion 142A. The suction chamber H1 is adapted to allowthe gaseous refrigerant to flow around the electric motor 160 and coolthe electric motor 160. Spaces on one side and the other side of theelectric motor 160 communicate with each other so as to form the singlesuction chamber H1. An appropriate amount of lubricant is stored in thesuction chamber H1 in order to lubricate sliding portions of componentsincluding the rotationally driven drive shaft 166. Accordingly, in thesuction chamber H1, the gaseous refrigerant flows in the form of a mixedfluid with lubricant.

The center housing 144 has a bottomed cylindrical shape having anopening on the side opposite to the side at which the front housing 142is fastened and is adapted to house the scroll unit 120 therein. Thecenter housing 144 has a cylindrical portion 144A and a bottom wallportion 144B provided at one end side of the cylindrical portion 144A.The scroll unit 120 is housed in a space defined by the cylindricalportion 144A and the bottom wall portion 144B. At the other end side ofthe cylindrical portion 144A, a fitting portion 144A1 to which the fixedscroll 122 is fitted is formed. Accordingly, the opening of the centerhousing 144 is closed by the fixed scroll 122. The bottom wall portion144B is formed such that a radially center portion thereof bulges towardthe electric motor 160. A through hole for receiving the other endportion of the drive shaft 166 penetrating therethrough is formed at aradially center portion of such a bulging portion 144B1 of the bottomwall portion 144B. Furthermore, a fitting portion for receiving abearing 200 fitted therein is formed on the side, closer to the scrollunit 120, of the bulging portion 144B1. The bearing 200 rotatablysupports the other end portion of the drive shaft 166.

A thin annular thrust plate 210 is disposed between the bottom wallportion 144B of the center housing 144 and the bottom plate 124A of theorbiting scroll 124. The bottom wall portion 144B receives, at an outerperipheral portion, a thrust force from the orbiting scroll 124 via thethrust plate 210. Seal members 220 are embedded in respective portions,in contact with the thrust plate 210, of the bottom wall portion 144Band the bottom plate 124A.

A back pressure chamber H4 is formed between an electric motor 160 sideend surface of the bottom plate 124A and the bottom wall portion 144B,i.e., between an end surface, opposite to the fixed scroll 122, of theorbiting scroll 124 and the center housing 144. The center housing 144is provided with a refrigerant introduction passage L1 formed so as tointroduce the gaseous refrigerant from the suction chamber H1 to a spaceH5 near the outer end portions of the wraps 122B and 124B of the scrollunit 120. Since the refrigerant introduction passage L1 allows the spaceH5 and the suction chamber H1 to communicate with each other, thepressure in the space H5 is equal to the pressure (suction pressure Ps)in the suction chamber H1.

The rear housing 146 is fastened to a fitting portion 144A1 side endportion of the cylindrical portion 144A of the center housing 144 withat least one fastener. Accordingly, the fixed scroll 122 is fixed withits bottom plate 122A held between the fitting portion 144A1 and therear housing 146. That is, the fixed scroll 122 is fixed to the housing140. The rear housing 146, which has a bottomed cylindrical shape havingan opening on the side fastened to the center housing 144, has acylindrical portion 146A and a bottom wall portion 146B provided at theother end portion of the cylindrical portion 146A.

The discharge chamber H2 for gaseous refrigerant is defined by thecylindrical portion 146A and the bottom wall portion 146B of the rearhousing 146, and the bottom plate 122A of the fixed scroll 122. Adischarge passage (discharge hole) L2 for gaseous refrigerant is formedat a central portion of the bottom plate 122A. The discharge passage L2is provided with a check valve 230 formed, for example, of a reed valve.The check valve 230 restricts the flow of the gaseous refrigerant fromthe discharge chamber H2 to the scroll unit 120. The gaseous refrigeranthaving been compressed in the compression chamber H3 of the scroll unit120 is discharged to the discharge chamber H2 through the dischargepassage L2 and via the check valve 230.

Although not illustrated in the drawings, an oil separator forseparating lubricant from the gaseous refrigerant in the dischargechamber H2 is disposed in the rear housing 146. The gaseous refrigerant,from which lubricant has been separated by the oil separator, isdischarged to the high-pressure side of the refrigeration circuit via adischarge port P2 formed on the bottom wall portion 146B of the rearhousing 146. On the other hand, the lubricant separated by the oilseparator is supplied to the back pressure chamber H4 through a backpressure supply passage L3, which is described later.

The electric motor 160 is, for example, a three-phase alternatingcurrent motor, and includes a rotor 162 and a stator core unit 164disposed radially outward of the rotor 162. The stator core unit 164 ofthe electric motor 160 is supplied with an alternating currentconverted, for example, from a direct current from an in-vehicle battery(not shown) by the inverter 180.

The rotor 162 is rotatably supported radially inside the stator coreunit 164 via the drive shaft 166 that is press-fitted into a shaft holeformed at a radially center of the rotor 162. The one end portion of thedrive shaft 166 is rotatably supported on the support portion 142B1 ofthe front housing 142 via a sliding bearing 240. The other end portionof the drive shaft 166 penetrates the through hole formed in the centerhousing 144 and is rotatably supported on the bearing 200. When power issupplied from the inverter 180, a magnetic field is generated in thestator core unit 164, and a torque acts on the rotor 162 to rotationallydrive the drive shaft 166. The other end portion of the drive shaft 166is connected to the orbiting scroll 124 via the conversion mechanism300.

The conversion mechanism 300 has a function to mutually convert a rotarymotion of the rotating main shaft (drive shaft 166 in this embodiment)and an orbiting motion of the orbiting scroll 124. The conversionmechanism 300 will be described in detail later, referring to FIGS. 3 to5 . In the present embodiment, the orbiting scroll 124 is disposed to becapable of revolving around the axis of the fixed scroll 122 via theconversion mechanism 300, in a state in which rotation of the orbitingscroll 124 is prevented. In addition, a balance weight (counterweight)290 that counteracts the centrifugal force of the orbiting scroll 124 isattached to the other end portion of the drive shaft 166.

FIG. 2 is a block diagram for illustrating flows of gaseous refrigerantand lubricant in the scroll compressor 100.

As illustrated in FIGS. 1 and 2 , low-pressure, low-temperature gaseousrefrigerant from the refrigerant circuit is introduced into the suctionchamber H1 via the suction port P1, and then is introduced into thespace H5 near the outer end portion of the scroll unit 120 through therefrigerant introduction passage L1. The gaseous refrigerant in thespace H5 is taken into the compression chamber H3 of the scroll unit 120and is compressed therein. After being compressed in the compressionchamber H3, the gaseous refrigerant is discharged into the dischargechamber H2 through the discharge passage L2 and via the check valve 230,and is then discharged to the high-pressure side of the refrigerationcircuit via the discharge port P2. In this way, the scroll unit 120 isconfigured to compress, in the compression chamber H3, the gaseousrefrigerant flowing therein via the suction chamber H1 and discharge thecompressed gaseous refrigerant via the discharge chamber H2.

Here, as illustrated in FIG. 1 , the scroll compressor 100 furtherincludes a back pressure control valve 400 for controlling a backpressure Pm in the back pressure chamber H4. The back pressure controlvalve 400, which is a mechanical (autonomous) pressure regulating valve,operates in accordance with a differential pressure between a dischargepressure Pd in the discharge chamber H2 and the back pressure Pm in theback pressure chamber H4 and thereby automatically adjusts the valveopening such that the back pressure Pm in the back pressure chamber H4approaches a target back pressure Pc. At the bottom wall portion 146B ofthe rear housing 146, the back pressure control valve 400 is stored in astorage chamber 146C formed to extend from an outer peripheral surfaceof the bottom wall portion 146B in a direction orthogonal to the axis ofthe drive shaft 166 of the electric motor 160.

As illustrated in FIGS. 1 and 2 , the scroll compressor 100 furtherincludes a back pressure supply passage L3, a pressure release passageL4, and a suction pressure sensing passage L5, in addition to therefrigerant introduction passage L1 and the discharge passage L2.

The back pressure supply passage L3 is formed in the rear housing 146and the center housing 144 such that the discharge chamber H2 and theback pressure chamber H4 communicate with each other. Here, the backpressure supply passage L3 in the rear housing 146 passes through thestorage chamber 146C storing the back pressure control valve 400. Thelubricant separated by the oil separator from the gaseous refrigerant inthe discharge chamber H2 is introduced into the back pressure chamber H4via the pressure control valve 400 and through the back pressure supplypassage L3 to lubricate each sliding portion and to increase the backpressure Pm in the back pressure chamber H4.

The back pressure control valve 400 is disposed midway of the backpressure supply passage L3 so as to constitute a part of the backpressure supply passage L3. Accordingly, the lubricant separated fromthe gaseous refrigerant in the discharge chamber H2 is supplied to theback pressure chamber H4 after being appropriately decompressed by theback pressure control valve 400 while passing through the back pressuresupply passage L3. That is, by adjusting the opening of the backpressure supply passage L3 connected to the inlet side (upstream side)of the back pressure chamber H4 using the back pressure control valve400, the flow rate of the lubricant entering the back pressure chamberH4 is increased or decreased, and thus, the back pressure Pm isregulated.

The pressure release passage L4 is penetratingly formed in the driveshaft 166 in its axial direction so as to allow the back pressurechamber H4 and the suction chamber H1 to communicate with each other. Anorifice OL is disposed midway of the pressure release passage L4, forexample, at a suction chamber H1 side end portion of the drive shaft166. Accordingly, the lubricant in the back pressure chamber H4 isreturned to the suction chamber H1 while its flow rate is restricted bythe orifice OL.

The suction pressure sensing passage L5 allows the space H5 near theouter end portion of the scroll unit 120 and the storage chamber 146C tocommunicate with each other, so as to sense the suction pressure Ps inthe suction chamber H1 at the back pressure control valve 400.Specifically, the suction pressure sensing passage L5 is formed in thebottom plate 122A of the fixed scroll 122 and in the rear housing 146.Although here the suction pressure sensing passage L5 indirectly sensesthe suction pressure Ps in the suction chamber H1 via the space H5, itmay directly sense the suction pressure Ps in the suction chamber H1.

Here, the back pressure chamber H4 (a mechanical chamber in which arevolving drive element such as the drive shaft 166 is provided) isformed on a back surface side of the orbiting scroll 124 (i.e., an endsurface side, opposite to the fixed scroll 122, of the orbiting scroll124). The back pressure chamber H4 generates the back pressure Pm thatpresses and biases the orbiting scroll 124 toward the fixed scroll 122.Thus, the orbiting scroll 124 is pressed toward the fixed scroll 122 bythe back pressure Pm in the back pressure chamber H4. Assume here thatthe scroll unit 120 performs compression operation in a state in whichthe resultant force of the back pressure Pm acting on the end surface,facing the back pressure chamber H4, of the bottom plate 124A of theorbiting scroll 124 is considerably less than the compression reactionforce acting on the end surface, facing the compression chamber H3, ofthe bottom plate 124A; that is, the scroll unit 120 performs compressionoperation with an insufficient back pressure. In such a case, a gap maybe formed between the tip of the wrap 124B of the orbiting scroll 124and the bottom plate 122A of the fixed scroll 122 and a gap may beformed between the bottom plate 124A of the orbiting scroll 124 and thetip of the wrap 122B of the fixed scroll 122. These gaps may reduce thevolumetric efficiency of the compressor. In order to avoid insufficientback pressure, when the back pressure Pm is less than the target backpressure Pc, the back pressure control valve 400 increases the backpressure Pm closer to the target back pressure Pc.

On the other hand, if the resultant force of the back pressure Pm in theback pressure chamber H4 is excessively greater than the compressionreaction force; that is, if the back pressure is excessive, thefrictional force between the fixed scroll 122 and the orbiting scroll124 excessively increases and thus reduces the machine efficiency of thecompressor. In order to avoid excessive back pressure, when the backpressure Pm exceeds the target back pressure Pc, the back pressurecontrol valve 400 reduces the back pressure Pm closer to the target backpressure Pc.

Next, the conversion mechanism 300 will be described in detail withreference to FIGS. 3 to 5 in addition to FIG. 1 . FIG. 3 is an enlargedcross-sectional view of the conversion mechanism 300. FIG. 4 is aperspective view of an eccentric bush (eccentric bushing) 270. FIG. 5 isa sectional view of the eccentric bush 270.

The conversion mechanism 300 includes an eccentric shaft (crankpin) 260,the eccentric bush 270, and a bearing 280. The eccentric shaft 260 isprovided on the other end surface of the drive shaft 166 and iseccentric (offset) with respect to the drive shaft 166. The eccentricbush 270 is in a cylindrical shape and has a through hole 271 into whichthe eccentric shaft 260 is fitted at a position eccentric from itscentral axis BS. Thus, the eccentric bush 270 is eccentrically attachedto the eccentric shaft 260 via the through hole 271.

The bearing 280 is press-fitted into a cylindrical boss portion 250formed to protrude on a back pressure chamber H4 side end surface of thebottom plate 124A of the orbiting scroll 124 and supports an outerperipheral surface 272 of the eccentric bush 270. In the presentembodiment, a sliding bearing is used as the bearing 280. Thus, theeccentric bush 270 is rotatably supported by an inner peripheral surfaceof the boss portion 250 via the bearing 280. In this way, the orbitingscroll 124 is capable of revolving around the axis of the fixed scroll122 via the conversion mechanism 300 in a state in which rotation of theorbiting scroll 124 is restricted.

A lubricant supply passage 350 for supplying lubricant to the bearing280 is penetratingly formed in the eccentric bush 270. The lubricantsupply passage 350 includes an axial flow passage 351 extending in anaxial direction of the eccentric bush 270 and a radial flow passage 352extending in a radial direction of the eccentric bush 270.

The axial flow passage 351 extends substantially in parallel to thecentral axis BS of the eccentric bush 270 and to a central axis RS ofthe drive shaft 166, and penetrates the eccentric bush 270. The radialflow page 352 branches from midway of the axial flow passage 351 andextends in the radial direction of the eccentric bush 270 to the outerperipheral surface 272 of the eccentric bush 270.

On an end surface of the eccentric bush 270, which is adjacent to theother end surface of the drive shaft 166, a concave portion 273 isformed extending in the radial direction of the eccentric bush 270. Anopening on one end side of the axial flow passage 351 is positioned on abottom surface of the concave portion 273. This opening can function asan inlet 355 of the lubricant supply passage 350. That is, the axialflow passage 351 has the inlet 355 of the lubricant supply passage 350.

An opening on one end of the radial flow passage 352, which ispositioned on the outer peripheral surface 272 of the eccentric bush270, can function as an outlet 356 of the lubricant supply passage 350.That is, the radial flow passage 352 has the outlet 356 of the lubricantsupply passage 350. The outlet 356 of the lubricant supply passage 350is facing an inner peripheral surface (support surface) 281 of thebearing 280. The outlet 356 of the lubricant supply passage 350 ispreferably disposed so as to face an axial center portion of the innerperipheral surface 281 of the bearing 280.

As illustrated in FIG. 5 , in the present embodiment, when the eccentricbush 270 is divided, by a first virtual plane PL1 including the centralaxis RS of the drive shaft 166, into a first region T1 and a secondregion T2, the first region T1 includes the central axis BS of theeccentric bush 270, the lubricant supply passage 350, and the thoughhole 271 positioned therein. The first virtual plane PL1 is a virtualplane perpendicular to a second virtual plane PL2 that includes both ofthe central axis RS of the drive shaft 166 and the central axis BS ofthe eccentric bush 270.

In the present embodiment, when a distance between the first virtualplane PL1 and the central axis BS of the eccentric bush 270 is definedas N1 and a distance between the first virtual plane PL1 and a centralaxis WS of the axial flow passage 351 is defined as N2, the relationshipof N1<N2 is satisfied. That is, the central axis WS of the axial flowpassage 351 is further away than the central axis BS of the eccentricbush 270 when viewed from the first virtual plane PL1. In addition, thelubricant supply passage 350 is further away than the central axis BS ofthe eccentric bush 270 when viewed from the first virtual plane PL1.

In the present embodiment, when a distance between the central axis RSof the drive shaft 166 and the central axis BS of the eccentric bush 270is defined as N3 and a distance between the central axis RS of the driveshaft 166 and the central axis WS of the axial flow passage 351 isdefined as N4, the relationship of N3<N4 is satisfied. That is, thecentral axis WS of the axial flow passage 351 is further away than thecentral axis BS of the eccentric bush 270 when viewed from the centralaxis RS of the drive shaft 166. In addition, the lubricant supplypassage 350 is further away than the central axis BS of the eccentricbush 270 when viewed from the central axis RS of the drive shaft 166.

Here, supply of a lubricant to the bearing 280 will be described withreference to FIGS. 1 and 3 to 5 .

A part of the lubricant in the back pressure chamber H4 flows throughthe concave portion 273 of the eccentric bush 270, and then flows intothe axial flow passage 351 via the inlet 355. Due to the centrifugalforce generated by the rotary motion of the drive shaft 166 around thecentral axis RS of the drive shaft 166, most of the lubricant in theaxial flow passage 351 reaches to the radial flow passage 352, and thenis supplied to the inner peripheral surface 281 of the bearing 280 viathe outlet 356. The present embodiment employs the aforementionedconfiguration of the lubricant supply passage 350 so as to effectivelyprovide an action of the centrifugal force.

According to the present embodiment, the scroll compressor 100 as anexample of a scroll fluid machine has, in the housing 140, the driveshaft (rotating main shaft) 166 that is rotatably provided, the fixedscroll 122 fixed to the housing 140, the orbiting scroll 124 that orbitswith respect to the fixed scroll 122, and the conversion mechanism 300that mutually converts the rotary motion of the drive shaft (rotatingmain shaft) 166 and the orbiting motion of the orbiting scroll 124. Theconverting mechanism 300 includes the eccentric shaft 260 that isprovided on the end surface of the drive shaft (rotating main shaft) 166and is eccentric with respect to the drive shaft (rotating main shaft)166, the eccentric bush 270 having the through hole 271 into which theeccentric shaft 260 is inter-fitted, and the bearing 280 that ispress-fitted into the boss portion 250 formed on the orbiting scroll 124and supports the outer peripheral surface 272 of the eccentric bush 270.The lubricant supply passage 350 for supplying the lubricant to thebearing 280 is penetratingly formed in the eccentric bush 270. Theoutlet 356 of the lubricant supply passage 350 is disposed on the outerperipheral surface 272 of the eccentric bush 270. This enables to supplythe lubricant directly to the bearing 280 from the outlet 356 of thelubricant supply passage 350, and thus, the lubricant can besatisfactorily supplied to the bearing 280.

Furthermore, according to the present embodiment, the outlet 356 of thelubricant supply passage 350 is facing the inner peripheral surface 281of the bearing 280. Thus, the lubricant can be satisfactorily suppliedto the inner peripheral surface 281 of the bearing 280.

Furthermore, according to the present embodiment, the lubricant supplypassage 350 includes the axial flow passage 351 extending in the axialdirection of the eccentric bush 270 and the radial flow passage 352extending in the radial direction of the eccentric bush 270. The axialflow passage 351 has the inlet 355 of the lubricant supply passage 350and the radial flow passage 352 has the outlet 356 of the lubricantsupply passage 350. Thus, the lubricant supply passage 350 can be formedeasily.

Furthermore, according to the present embodiment, the lubricant supplypassage 350 is further away than the central axis BS of the eccentricbush 270 when viewed from the central axis RS of the drive shaft(rotating main shaft) 166. Thus, the lubricant can be positivelysupplied to the bearing 280 by means of the centrifugal force generatedby the rotational movement of the drive shaft 166.

Furthermore, according to the present embodiment, when the eccentricbush 270 is divided, by the first virtual plane PL1 including thecentral axis RS of the drive shaft (rotating main shaft) 166, into thefirst region T1 and the second region T2, the first region T1 includesthe central axis BS of the eccentric bush 270, the lubricant supplypassage 350, and the though hole 271 positioned therein. The lubricantsupply passage 350 is further away than the central axis BS of theeccentric bush 270 when viewed from the first virtual plane PL1. Thus,the lubricant can be positively supplied to the bearing 280 by means ofthe centrifugal force generated by the rotary motion of the drive shaft166.

Furthermore, according to the present embodiment, the scroll compressor100 as an example of a scroll fluid machine further includes the backpressure chamber H4 that is formed on the back surface side of theorbiting scroll 124 and generates the back pressure that presses andbiases the orbiting scroll 124 toward the fixed scroll 122. The outlet355 of the lubricant supply passage 350 communicates with the backpressure chamber H4. Thus, the lubricant in the back pressure chamber H4can be easily supplied to the bearing 280.

Furthermore, according to the present embodiment, the inlet 355 of thelubricant supply passage 350 is disposed at the concave portion 273formed on the end surface of the eccentric bush 270. Thus, the lubricantfrom the back pressure chamber H4 can be easily guided to the lubricantsupply passage 350.

Furthermore, according to the present embodiment, a sliding bearing isused as the bearing 280. Thus, the eccentric bush 270 can be rotatablysupported with simple structure.

Next, a second embodiment of the present invention will be describedreferring to FIG. 6 .

FIG. 6 is an enlarged cross-sectional view of the conversion mechanism300 according to the second embodiment.

The following will describe differences from the first embodimentdescribed above.

The eccentric bush 270 is integrally provided with a balance weight(counterweight) 290′. The balance weight 290′ is disposed at theopposite side of the through hole 271 with the central axis RS of thedrive shaft 166 therebetween. Also in such an eccentric bush 270 that isintegrally provided with the balance weight 290′, the lubricant supplypassage 350 similar to the above is preferably provided.

Note that in the above described first and second embodiments, thebalance weight 290, 290′ may be omitted.

Although the case in which the scroll fluid machine according to thepresent invention is a scroll compressor has been described in the abovefirst and second embodiments, it is apparent that the present inventionis also applicable to a scroll expander. When the present invention isapplied to a scroll expander, the scroll expander may be configured, forexample, to be incorporated in a refrigerant circuit of a Rankine cyclesystem for a vehicle to generate power by expanding refrigerant providedfrom the refrigerant circuit (recovering power from the refrigerant). Inaddition, when the present invention is applied to a scroll expander,the above described drive shaft 166 functions as an output shaft. Thatis, when the scroll fluid machine according to the present invention isa scroll compressor, the “rotating main shaft” of the present inventionfunctions as a drive shaft, and when the scroll fluid machine accordingto the present invention is a scroll expander, the “rotating main shaft”of the present invention functions as an output shaft.

The preferred embodiments of the present invention have been describedabove. However, the present invention is not limited to the embodimentsdescribed above, and further modification or other variations may bemade based on the technical concept of the present invention.

REFERENCE SYMBOL LIST

-   -   100 Scroll compressor (Scroll fluid machine)    -   122 Fixed scroll    -   124 Orbiting scroll    -   140 Housing    -   166 Drive shaft (Rotating main shaft)    -   250 Boss portion    -   260 Eccentric shaft    -   270 Eccentric bush    -   271 Through hole    -   272 Outer peripheral surface    -   273 Concave portion    -   280 Bearing    -   290, 290′ Balance weight    -   281 Inner peripheral surface    -   300 Conversion mechanism    -   350 Lubricant supply passage    -   351 Axial flow passage    -   352 Radial flow passage    -   355 Inlet    -   356 Outlet    -   BS, RS, WS Central axis    -   H4 Back pressure chamber    -   PL1 First virtual plane    -   PL2 Second virtual plane    -   T1 First region    -   T2 Second region

1. A scroll fluid machine comprising, in a housing: a rotating mainshaft that is rotatably provided; a fixed scroll fixed to the housing;an orbiting scroll that orbits with respect to the fixed scroll; and aconversion mechanism that mutually converts a rotary motion of therotating main shaft and an orbiting motion of the orbiting scroll,wherein the conversion mechanism includes: an eccentric shaft that isprovided on an end surface of the rotating main shaft and is eccentricwith respect to the rotating main shaft; an eccentric bush that has athough hole into which the eccentric shaft is fitted; and a bearing thatis press-fitted into a boss portion formed on the orbiting scroll andsupports an outer peripheral surface of the eccentric bush, wherein alubricant supply passage for supplying a lubricant to the bearing ispenetratingly formed in the eccentric bush, and wherein an outlet of thelubricant supply passage is disposed on the outer peripheral surface ofthe eccentric bush.
 2. The scroll fluid machine according to claim 1,wherein the outlet of the lubricant supply passage faces an innerperipheral surface of the bearing.
 3. The scroll fluid machine accordingto claim 1, wherein the lubricant supply passage includes an axial flowpassage extending in an axial direction of the eccentric bush and aradial flow passage extending in a radial direction of the eccentricbush, wherein the axial flow passage has an inlet of the lubricantsupply passage, and wherein the radial flow passage has the outlet ofthe lubricant supply passage.
 4. The scroll fluid machine according toclaim 1, wherein the lubricant supply passage is further away than acentral axis of the eccentric bush when viewed from a central axis ofthe rotating main shaft.
 5. The scroll fluid machine according to claim1, wherein, when the eccentric bush is divided, by a virtual planeincluding a central axis of the rotating main shaft, into a first regionand a second region, the first region includes a central axis of theeccentric bush, the lubricant supply passage, and the through holepositioned therein.
 6. The scroll fluid machine according to claim 5,wherein the lubricant supply passage is further away than the centralaxis of the eccentric bush when viewed from the virtual plane.
 7. Thescroll fluid machine according to claim 1, further comprising a backpressure chamber that is formed on a back surface side of the orbitingscroll and generates a back pressure that presses and biases theorbiting scroll toward the fixed scroll, wherein an inlet of thelubricant supply passage communicates with the back pressure chamber. 8.The scroll fluid machine according to claim 1, wherein an inlet of thelubricant supply passage is disposed on a concave portion formed on anend surface of the eccentric bush.
 9. The scroll fluid machine accordingto claim 1, wherein a sliding bearing is used as the bearing.